JP6991627B1 - Structure containing hydrophilic coating composition and hydrophilic coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a hydrophilic coating which does not deteriorate the function of the undercoat film and can be easily formed on the undercoat film. The present invention also provides a structure comprising such a hydrophilic coating. SOLUTION: The composition for hydrophilic coating of the present invention is a composition for hydrophilic coating containing colloidal silica and a thickener, and when a coating having a thickness of 10 μm is formed on a white substrate, The color difference ΔE * before and after coating the white substrate is 0.50 or less, and the viscosity measured according to JIS K5600-2-2 using a stormer viscometer is in the range of 40 to 120 KU. Further, the structure of the present invention is a structure including a substrate, a base coating film, and a coating with the above-mentioned hydrophilic coating composition, and the base coating film is a heat-shielding coating film. [Selection diagram] Fig. 1

Description

The present invention relates to a composition for a hydrophilic coating. The present invention also relates to a structure comprising a hydrophilic coating.

It is known to form a photocatalytic coating with titanium oxide in order to impart antifouling properties to buildings and the like. Although such a photocatalytic coating can impart high antifouling property, there is a problem that coating unevenness is likely to occur and it is difficult to apply.

As another antifouling coating, a hydrophilic coating using colloidal silica is known. Even if dirt adheres to the surface on which the hydrophilic coating is formed, it can be easily washed out by rain or the like.

Patent Document 1 discloses a composition for a hydrophilic coating containing a swellable layered silicate, colloidal silica, and a cross-linking agent. The paint described in Patent Document 1 contains a swellable layered silicate in a specific amount to improve the hydrophilicity of the coating and improve stain resistance, weather resistance and temperature water resistance.

Japanese Unexamined Patent Publication No. 2014-0701138

An object of the present invention is to provide a composition for a hydrophilic coating which does not deteriorate the function of the undercoat film and is easy to form on the undercoat film. It is also an object of the present invention to provide a structure comprising such a hydrophilic coating.

The present inventors have found that the above-mentioned problems can be solved by the present invention having the following aspects.
<< Aspect 1 >>
A composition for a hydrophilic coating containing colloidal silica and a thickener.
When a coating with a thickness of 10 μm is formed on a white substrate, the color difference ΔE ^* before and after application of the white substrate is 0.50 or less, and conforms to JIS K5600-2-2 using a Stormer viscometer. The viscosity measured in the above range is in the range of 40 to 120 KU.
Composition for hydrophilic coating.
<< Aspect 2 >>
The composition for hydrophilic coating according to aspect 1, wherein the thickener is a swellable layered silicate or a water-soluble polymer.
<< Aspect 3 >>
The hydrophilic coating composition according to aspect 2, wherein the thickener is a synthetic smectite.
<< Aspect 4 >>
The composition for hydrophilic coating according to aspect 2, wherein the thickener is hydroxyethyl cellulose.
<< Aspect 5 >>
The composition for hydrophilic coating according to any one of aspects 1 to 4, wherein the colloidal silica is contained in an amount of 2 to 10% by mass in a solid content concentration.
<< Aspect 6 >>
The hydrophilic coating composition according to any one of aspects 1 to 5, further comprising a water-soluble dye.
<< Aspect 7 >>
A structure comprising a substrate, an undercoat film, and a coating with the hydrophilic coating composition according to any one of aspects 1 to 6, wherein the undercoat film is a heat-shielding coating film. body.

According to the present invention, it is possible to provide a composition for hydrophilic coating which does not deteriorate the function of the undercoat film and is easy to form on the undercoat film. Further, according to the present invention, it is possible to provide a structure including such a hydrophilic coating.

FIG. 1 shows the results of a coating test using the hydrophilic coating compositions of Examples 1 and Reference Examples. FIG. 2 shows the results of an exposure test of a coating with the hydrophilic coating composition of Example 1.

<< Composition for hydrophilic coating >>
The composition for hydrophilic coating contains colloidal silica and a thickener, and has high transparency and relatively high viscosity. In the composition for hydrophilic coating, when a coating having a thickness of 10 μm is formed on a white substrate, the color difference ΔE ^* before and after coating the white substrate is 0.50 or less, and a Stormer viscometer is used. The viscosity measured according to JIS K5600-2-2 is in the range of 40 to 100 KU.

Conventionally, a heat-shielding coating film used for a roof of a building or the like has been used on the outermost surface to improve the heat-shielding property. However, as a result of studies by the present inventors, it was found that the stains adhering to the heat-shielding coating film have a non-negligible effect on the heat-shielding performance of the coating film. Therefore, as a result of further studies by the present inventors, if the above-mentioned hydrophilic coating composition is used, even if a coating is formed on the heat-shielding coating film, the function of the heat-shielding coating film is not affected, and the heat-shielding coating film is shielded. It was found that the coating film can be formed on the thermal coating film with less uneven coating, the stains are less likely to adhere, and even if the stains adhere, they can be easily washed away by rain or the like. On the other hand, in the hydrophilic coating composition described in Patent Document 1, the coating is partially clouded as described in the examples thereof, so that light irradiation such as a heat-shielding coating film is important. It was found to be ineffective in forming a coating on the underlying coating.

In the composition for hydrophilic coating, when a coating having a thickness of 10 μm is formed on a white substrate, the color difference ΔE ^* before and after coating the white substrate is 0.50 or less, 0.40 or less, 0.30 or less. , 0.25 or less, 0.20 or less, 0.15 or less, or 0.10 or less. Here, as the white substrate, a white coating film having a dry film thickness of 50 μm (Miracool Farm, Miracool Co., Ltd.) formed on a coating hiding rate test paper is used. The color difference ΔE ^* can be obtained by measuring the L ^* a ^* b ^* values before and after the formation of the hydrophilic coating using a color difference meter CR-410 manufactured by Konica Minolta Co., Ltd. and calculating from those values. can. When the composition for hydrophilic coating contains a water-soluble dye, this color difference ΔE ^* is measured in a state where there is no influence of coloring by the dye, for example, a state after the dye is faded after the coating is formed. ..

The coating with the composition for hydrophilic coating may have a haze of 50% or less, 30% or less, 20% or less, 15% or less, 10% or less, or 5% or less. Hayes coats a hydrophilic coating composition on a glass substrate and dries it at a temperature of 0 to 80 ° C. for 60 minutes to 10 days to form a coating. About this coating, haze meter NDH7000II (manufactured by Nippon Denshoku Kogyo Co., Ltd.) It can be measured by using or the like.

The composition for hydrophilic coating has a viscosity measured in accordance with JIS K5600-2-2 at 25 ° C. using a stoma viscometer in the range of 40 KU to 120 KU. As a stormer viscometer, specifically, using the Brookfield Digital Stormer Viscometer KU-3 available from Eiko Seiki Co., Ltd., and using the Krebs standard rotor KU-1030, the rotor is 100 in about 30 seconds. The viscosity can be measured by rotating it. This viscosity may be 40 KU or more, 42 KU or more, 45 KU or more, 49 KU or more, 50 KU or more, 55 KU or more, or 60 KU or more, 120 KU or less, 110 KU or less, 100 KU or less, 90 KU or less, 80 KU or less, 70 KU or less, or It may be 60 KU or less. This viscosity may be, for example, 42 KU to 100 KU, 45 KU to 70 KU, or 49 KU to 60 KU. With a viscosity in such a range, it becomes easy to form a thin and uniform coating on the underlying coating film. If the viscosity is too high, the coating tends to form thicker, which may reduce transparency, take longer to dry, and pose an economic problem. In the present specification, when the measured value is likely to vary, the measurement can be performed 10 times or more and the average value can be adopted as the measured value.

Further, the composition for hydrophilic coating was prepared by using a Brookfield B-type viscometer RV / DVE available from Eiko Seiki Co., Ltd. at 25 ° C., and the spindle No. The viscosity of 5 (RV-5) measured under the condition of 6 rpm may be 500 mPa · s or more, 1000 mPa · s or more, 2000 mPa · s or more, 3000 mPa · s or more, 30,000 mPa · s or less, 20000 mPa · s or less. It may be 10,000 mPa · s or less, 8000 mPa · s or less, or 5000 mPa · s or less. This viscosity may be, for example, 500 mPa · s to 30,000 mPa · s, or 2000 mPa · s to 10000 mPa · s. The viscosity measured under the condition of 60 rpm may be 300 mPa · s or more, 500 mPa · s or more, or 1000 mPa · s or more, and may be 8000 mPa · s or less, 5000 mPa · s or less, 3000 mPa · s or less, 2000 mPa · s. It may be less than or equal to 1000 mPa · s or less. This viscosity may be, for example, 300 mPa · s to 8000 mPa · s, or 300 mPa · s to 2000 mPa · s.

For example, when the thickener of the hydrophilic coating composition is an inorganic thickener, the viscosity measured under the above conditions at 6 rpm is 2000 mPa · s or more, 2500 mPa · s or more, or 3000 mPa · s or more. It may be 20000 mPa · s or less, 15000 mPa · s or less, 10000 mPa · s or less, 8000 mPa · s or less, or 5000 mPa · s or less. This viscosity may be, for example, 2000 mPa · s to 20000 mPa · s, or 3000 mPa · s to 10000 mPa · s. In that case, the viscosity measured under the above conditions at 60 rpm may be 300 mPa · s or more, 400 mPa · s or more, or 500 mPa · s or more, 3000 mPa · s or less, 2000 mPa · s or less, 1500 mPa · s. It may be less than or equal to 1000 mPa · s or less. This viscosity may be, for example, 300 mPa · s to 3000 mPa · s, or 300 mPa · s to 1000 mPa · s.

For example, when the thickener of the composition for hydrophilic coating is an organic thickener, the viscosity measured under the above conditions at 6 rpm is 500 mPa · s or more, 1000 mPa · s or more, or 2000 mPa · s or more. It may be 30,000 mPa · s or less, 20000 mPa · s or less, 10,000 mPa · s or less, 8000 mPa · s or less, or 5000 mPa · s or less. This viscosity may be, for example, 500 mPa · s to 30,000 mPa · s, or 500 mPa · s to 10000 mPa · s. In that case, the viscosity measured under the above conditions at 60 rpm may be 300 mPa · s or more, 500 mPa · s or more, or 1000 mPa · s or more, and 8000 mPa · s or less, 5000 mPa · s or less, 3000 mPa · s. Hereinafter, it may be 2000 mPa · s or less, or 1000 mPa · s or less. This viscosity may be, for example, 300 mPa · s to 10000 mPa · s, or 300 mPa · s to 5000 mPa · s.

The composition for hydrophilic coating can have thixotropic properties, whereby a coating can be easily formed on the undercoat film. The thixotropic property can be evaluated from the ratio (TI value) of the viscosity measured at 6 rpm to the viscosity measured at 60 rpm using the viscosity measured under the above measurement conditions. The TI value (viscosity measured at 6 rpm / viscosity measured at 60 rpm) of the composition for hydrophilic coating may be 1.0 or more, 3.0 or more, 5.0 or more, or 8.0 or more. It may be 12.0 or less, 10.0 or less, 8.0 or less, 5.0 or less, or 3.0 or less. This TI value may be, for example, 1.0 to 12.0 or 3.0 to 10.0.

For example, when the thickener of the composition for hydrophilic coating is an inorganic thickener, the thixotropic property may be 5.0 or more, 7.0 or more, or 8.0 or more, and 12.0. Hereinafter, it may be 11.0 or less, or 10.0 or less. This thixotropic property may be, for example, 5.0 to 12.0 or 7.0 to 11.0.

For example, when the thickener of the composition for hydrophilic coating is an organic thickener, the thixotropic property may be 1.0 or more, 1.5 or more, 2.0 or more, or 3.0 or more. It may be 5.0 or less, 4.0 or less, 3.0 or less, or 2.0 or less. This thixotropic property may be, for example, 1.0 to 5.0, or 1.5 to 3.0.

The coating with the composition for hydrophilic coating may have a static contact angle with pure water of 50 ° or less, 30 ° or less, 25 ° or less, 22 ° or less, 20 ° or less, or 15 ° or less. As a result, it has very high hydrophilicity and can impart high antifouling property to the coating. To measure the static contact angle, for example, a hydrophilic coating composition is coated on a glass substrate and dried at a temperature of 0 to 80 ° C. for 60 minutes to 10 days to form a coating, and the contact angle meter DMo is used for this coating. It can be measured using -501 (manufactured by Kyowa Interface Science Co., Ltd.) or the like.

The composition for hydrophilic coating does not need to contain an emulsion-based resin binder, for example, an acrylic emulsion-based binder, and even if it is contained, it may be 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less. can do.

<Coroidal silica>
By including colloidal silica in the composition for hydrophilic coating, a hydrophilic layer of hydroxyl groups is formed on the surface of the coating when the coating is formed, whereby the coating can be made antifouling.

As the colloidal silica, water-dispersed colloidal silica is preferable from the viewpoint of the environment. Water-dispersed colloidal silica is silica particles dispersed in an aqueous medium. Further, there are various types of colloidal silica, and the colloidal silica is not particularly limited, but substantially spherical silica particles having an average particle diameter of 5 to 100 nm, which are observed and measured by an electron microscope, are dispersed in the medium. Type, a type in which silica particles aggregated in a chain shape having a thickness of 5 to 50 nm and a length of about 40 to 400 nm are dispersed in a medium, and spherical silica particles having an average particle diameter of 10 to 50 nm are in the shape of a pearl necklace having a length of 50 to 400 nm. Examples thereof include a pearl necklace-like type in which those connected to the above are dispersed in a medium, and an annular type in which silica particles having an average particle diameter of 5 to 50 nm are annularly aggregated and dispersed in the medium. From the viewpoint of antifouling property, colloidal silica in which spherical silica particles are dispersed in a medium can be used. Further, the silica particles in colloidal silica preferably have an average particle diameter of 5 to 100 nm or 8 to 20 nm. Within this range, antifouling property, stability and the like tend to be good.

Examples of colloidal silica in which substantially spherical or spherical silica particles are dispersed in water include Snowtex-20, Snowtex-O, Snowtex-C, and Snowtex-S manufactured by Nissan Chemical Industries, Ltd. Examples thereof include Adelite AT-20, AT-20N, AT-20A and AT-300 manufactured by ADEKA. Examples of the chain-type colloidal silica in which silica particles aggregated in a chain are dispersed in water include Snowtex-UP and Snowtex-OUP manufactured by Nissan Chemical Industries, Ltd. Examples of the pearl necklace-shaped colloidal silica in which spherical silica particles connected in the shape of a pearl necklace are dispersed in a medium include Snowtex-PS-S, Snowtex-PS-M, and Snowtex-manufactured by Nissan Chemical Industries, Ltd. Examples include PS-SO and Snowtex-PS-MO.

In the composition for hydrophilic coating, the solid content of colloidal silica in the total solid content may be 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, or 80% by mass or more. , 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less. For example, the solid content of colloidal silica in the total solid content may be 60% by mass or more and 95% by mass or less, or 65% by mass or more and 90% by mass or less.

In the composition for hydrophilic coating, the solid content of colloidal silica may be 1% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more, and 15% by mass or less, 10% by mass. It may be mass% or less, 8 mass% or less, or 6 mass% or less. For example, the solid content of colloidal silica may be 1% by mass or more and 15% by mass or less, or 2% by mass or more and 10% by mass or less.

<Thickener>
The composition for hydrophilic coating contains a thickener and is relatively viscous as described above. The present inventors can form a coating relatively uniformly even on a resin-based coating film when the colloidal silica-based coating composition contains a thickener and has sufficient viscosity. I found. When the thickener was not contained, the coating could not be uniformly formed on the resin-based coating film of the silicone-based resin.

The type of thickener is not particularly limited, and may be an inorganic thickener or an organic thickener. Examples of the inorganic thickener include an inorganic thickener that swells in water to increase the viscosity, and examples thereof include swellable clay, particularly swellable layered silicate. Further, examples of the organic thickener include an organic thickener that dissolves in water to increase the viscosity, and examples thereof include a water-soluble polymer.

Examples of the swelling layered silicate include smectite clay minerals such as montmorillonite, saponite, hectorite, byderite, stepnsite, and nontronite, vermiculite, halloysite, and swelling mica (mica). Among these, swellable layered silicates of synthetics, such as synthetic smectites, rather than natural ones, can be mentioned in particular. The swellable layered silicate of the composite is preferred because it has less impurities and can increase the transparency of the coating.

When an inorganic thickener is used, its content may be 1.0% by mass or more, 1.5% by mass or more, or 2.0% by mass or more, and 5.0% by mass or less. It may be 0% by mass or less, 2.5% by mass or less, or 2.0% by mass or less. For example, the content of the inorganic thickener may be 1.0% by mass or more and 5.0% by mass or less, or 1.5% by mass or more and 3.0% by mass or less.

Water-soluble polymers include Arabic gum, succinoglycan, welan gum, tragacanto gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, caseinc santan gum, dextran, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, starch glycolic acid. Sodium, Alginic acid propylene glycol ester, Polyvinyl alcohol, Polyvinylpyrrolidone, Polyvinylmethyl ether, Sodium polyacrylate, Carboxyvinyl polymer, Polyethylene oxide, Copolymer of vinyl acetate and polyvinylpyrrolidone, Crosslinked acrylic acid polymer, Polystyrene acrylic acid Examples include salts of polymers.

When an organic thickener is used, its content may be 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more, and 2.0% by mass or less. It may be 5% by mass or less, 1.0% by mass or less, or 0.8% by mass or less. For example, the content of the organic thickener may be 0.1% by mass or more and 2.0% by mass or less, or 0.3% by mass or more and 1.0% by mass or less.

<Water-soluble dye>
The hydrophilic coating composition may further contain a water-soluble dye. Also, in another embodiment, the hydrophilic coating composition comprises colloidal silica and a water-soluble dye.

When the coating is formed by a composition that does not contain a water-soluble dye, it is quite difficult to determine whether or not the coating can be formed uniformly and evenly because the coating is transparent. However, when the water-soluble dye is contained, it is advantageous to include the water-soluble dye in the hydrophilic coating composition because it can be seen at a glance whether or not the coating has uneven coating. It was also found that when colloidal silica contains a water-soluble dye, only the water-soluble dye can be easily washed out with water after the coating is formed. Therefore, a colorless and transparent coating can be obtained by washing the water-soluble dye from the coating with water or rain after forming a colored coating containing the water-soluble dye.

The water-soluble dye is not particularly limited as long as it can be easily washed out with water from the coating, but well-known dyes such as direct dyes, acid dyes and basic dyes can be used, and are used for foods, industries, textiles and the like. Dyes for various purposes can be used. Among these, edible dyes are highly safe and can be faded by ultraviolet rays. Therefore, it is possible to fade the coloring with sunlight without washing the coating with water, which is preferable. Further, even when it is washed away with water, it is preferable because it has a low environmental load. Among the edible dyes, a blue edible dye such as Blue No. 1 is preferable because it can give a clean appearance to the hydrophilic coating composition. In the present specification, the "edible dye" means a dye that can also be used for foods. For example, Blue No. 1 is known to be used in foods, but it is also used in medicines, cosmetics, and the like.

The color of the dye is not limited to blue as described above, and may be any color that can be visually recognized when the coating is formed. For example, blue, green, yellow, orange, red, purple, etc. can be mentioned, and specifically, blue No. 1, blue No. 2, green No. 3, yellow No. 4, and yellow, which are known as edible dyes. No. 5, Red No. 2, Red No. 3, Red No. 40, Red No. 102, Red No. 104, Red No. 105, Red No. 106, etc., or a combination thereof can be used.

The content of the water-soluble dye is not particularly limited as long as it can exhibit the above functions, but may be 0.005% by mass or more, 0.01% by mass or more, or 0.02% by mass or more. It may be 0.3% by mass or less, 0.2% by mass or less, 0.1% by mass or less, or 0.05% by mass or less. For example, the content of the water-soluble dye may be 0.005% by mass or more and 0.3% by mass or less, or 0.01% by mass or more and 0.1% by mass or less.

<Other ingredients>
The composition for hydrophilic coating may further contain other components. For example, the composition for hydrophilic coating may include ion-exchanged water, a solvent, a defoaming agent, a plasticizer, an antifreeze agent, a drying accelerator, an ultraviolet absorber, a surfactant, a curing agent, a cross-linking agent and the like. Is not limited to these. However, these may not be substantially contained.

《Hydrophilic coating》
The hydrophilic coating can be formed by applying the above hydrophilic coating composition. This coating can have antifouling properties and can wash away dirt adhering to the surface with water.

"Structure"
The structure includes the substrate, the undercoat, and the coating with the above hydrophilic coating composition in this order. The structure is preferably a building, but is not limited to this, and may be a vehicle body or the like.

In order to form the undercoat film on the substrate, the undercoat may be applied onto the substrate by a brush, a roller, a spray or the like. Similarly, a brush, roller, spray or the like can be used to form a coating on the underlying coating.

<Hypokeimenon>
The base of the structure is, for example, a building such as a building, a house, a wall, a soundproof wall of a highway; a roof of various structures such as various structures made of iron, concrete, etc. installed in bridges, parks, etc. An outer wall surface can be exemplified. Examples of the outer wall surface include general outer wall materials, for example, inorganic exterior materials such as ceramic siding boards, mortar, concrete, and slate; metal materials such as iron, aluminum, and metal siding. Exterior material; Wood-based exterior materials such as natural wood and plywood can be mentioned.

<Undercoat film>
The undercoat film is not particularly limited as long as it can function as an undercoat film while being protected by a transparent coating, and examples thereof include a heat-shielding coating film formed by a heat-shielding paint.

The heat-shielding paint is a paint for suppressing the temperature rise by reflecting sunlight, and includes solvent-based paints including heat-shielding materials, inorganic paints, organic-inorganic composite paints, weak solvent-based paints, and various water-based paints. Can be used. Here, the weak solvent-based paint uses a mineral spirit called a weak solvent, an aliphatic hydrocarbon, or the like as a main solvent, forms a coating film at room temperature, and has adhesion to a wide range of substrates. There are features such as. Examples of the binder resin for the paint include one or more kinds of paints made of acrylic resin, urethane resin, silicone resin, fluororesin and the like.

Among these, it has been found that the above-mentioned composition for hydrophilic coating is particularly advantageous because it can form a uniform coating even for a heat-shielding paint containing a silicone-based resin as a binder. .. In the present specification, the silicone-based resin is not particularly limited as long as it is a silicone-based resin used in the field of paints, and includes not only silicone resins but also other silicone-modified resins. Examples of other silicone-modified resins include silicone-modified acrylic resins, silicone-modified polyurethane resins, silicone-modified polyester resins, silicone-modified alkyd resins, and silicone-modified epoxy resins. Further, an organic resin-modified silicone resin can also be mentioned, and examples thereof include an epoxy-modified silicone resin, a polyester-modified silicone resin, and an alkyd resin-modified silicone resin. Such a silicone-based resin usually has water repellency, and it is usually difficult to uniformly apply the hydrophilic coating composition evenly. Specific examples of such a heat-shielding paint include Miracool Farm, which is a water-based paint, and Miracool S100, which is a weak solvent-based paint.

As the heat-shielding material contained in the heat-shielding paint, a heat-shielding material conventionally used in the heat-shielding paint can be used, and for example, a heat-shielding material pigment and / or hollow particles can be used.

The heat-shielding pigment that can be used as the heat-shielding material of the heat-shielding paint is not particularly limited to an inorganic pigment or an organic pigment as long as it can reflect at least near infrared rays. For example, white pigments include titanium oxide and zinc oxide pigments, black pigments include manganese ittrium black pigments, and yellow pigments include azo pigments and benzoimidazolone pigments. As the red pigment, a quinacridone pigment can be mentioned, and as a blue pigment, a copper phthalocyanine blue pigment can be mentioned. The heat-shielding paint can contain one or more pigments selected from these pigments.

Examples of the hollow particles that can be used as the heat-shielding material of the heat-shielding paint include transparent or translucent ceramic hollow particles. Examples of such ceramic hollow particles include hollow particles such as a zirconia-titania composite, a silicon borate ceramic, a shirasu balloon, and a glass balloon. The particle diameter of the hollow particles can be in the range of 5 μm or more and 150 μm or less, or 30 μm or more and 100 μm or less. It is more effective from the point of view.

The content of the heat-shielding material contained in the heat-shielding paint is, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, or 30% by mass. It may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 15% by mass or less. For example, the content of the heat-shielding material contained in the heat-shielding paint may be 1% by mass or more and 50% by mass or less, or 10% by mass or more and 30% by mass or less.

<Other layers>
The structure may have other layers other than the above, and may have, for example, a primer layer well known in the art between the substrate and the undercoat film.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

<< Manufacturing example >>
25 parts by mass of colloidal silica (Snowtex C: water-dispersed colloidal silica, average particle size 10 to 20 nm, Nissan Chemical Industries, Ltd.) was added to a container containing 59.10 parts by mass of ion-exchanged water, and the mixture was further stirred. Hydroxyethyl cellulose (SP-900, Daicel FineChem Co., Ltd.) as a thickener was gradually added and further mixed. Then, 0.015 parts by mass of Blue No. 1 was added as a colorant and further mixed to obtain the composition for hydrophilic coating of Example 1.

The composition for hydrophilic coating of Example 2 in the same manner as in Example 1 except that synthetic smectite (Smecton SA, Kunimine Industries, Ltd.), which is an inorganic thickener, was used instead of the organic thickener. Got

The hydrophilic coating composition of Reference Example was obtained in the same manner except that the thickener was not added.

《Measurement of physical properties》
<Transparency: ΔE ^* Measurement>
A white paint was applied over the white and black parts of the coating concealment test paper to a thickness of about 50 μm in terms of dry film thickness. The L ^* a ^* b ^* value of the coating film of the white paint was measured using a colorimeter CR-410 manufactured by Konica Minolta Co., Ltd. Then, using the compositions of each of the above examples, a coating of about 5 to 20 μm was formed, and the L ^* a ^* b ^* value was further measured on the coating. After the coating was formed and before the measurement, the colorant was washed away.

The results are shown in Table 1.

As can be seen from this result, each coating has a low ΔE ^* value before and after the formation of the coating, and is extremely transparent.

<Transparency: Transmittance measurement>
A coating with a thickness of about 5-20 μm is formed on 2 mm float glass to obtain total light transmittance (TT), parallel line transmittance (PT), haze, and diffuse transmittance (DIF). , Haze meter NDH7000II (manufactured by Nippon Denshoku Kogyo Co., Ltd.) and the like. As a reference, the transmittance of only the float glass was also measured.

The results are shown in Table 2.

<viscosity>
The viscosity of the composition for hydrophilic coating was measured at 25 ° C. using a stoma viscometer according to JIS K5600-2-2. The viscosity was measured using the Brookfield Digital Viscometer KU-3 available from Hidehiro Seiki Co., Ltd. as a stormer viscometer. In addition, using the Brookfield B-type viscometer RV / DVE available from Hideko Seiki Co., Ltd., the spindle NO. The viscosity of 5 (RV-5) was measured under the conditions of 6 rpm and 60 rpm, and the TI value was also calculated.

The results are shown in Table 3.

<Static contact angle>
For the coating formed on the silicone rubber, the static contact angle with water was measured using DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.) or the like.

Table 4 shows the results of the average values when the measurements were performed three times.

<< Application test >>
Example 1 in which a coating film of a weak solvent-based heat-shielding paint (Miracool S100, Miracool Co., Ltd.) containing a silicone-based resin as a binder is formed on a base material, and 0.5 parts by mass of a thickener is contained therein. A coating was formed using the composition for hydrophilic coating of. Similarly, a coating is formed using the hydrophilic coating composition of Example 2 containing 2.0 parts by mass of a thickener, and similarly, a coating is formed using the hydrophilic coating composition of Reference Example. did.

FIG. 1 shows photographs of the state of Example 1 and Reference Example immediately after the coating was formed and before the coating was decolorized. As shown in FIG. 1, the coating film according to Example 1 was able to be formed relatively uniformly on the coating film, whereas the coating film according to Reference Example had large coating unevenness. The coating of Example 2 could be formed relatively uniformly on the coating film as in Example 1.

《Exposure test》
A coating film made of a weak solvent-based heat-shielding paint (Miracool S100, Miracool Co., Ltd.) containing a silicone-based resin as a binder is formed on the base material, and 0.5 parts by mass of a thickener is contained in only half of the area. A coating was formed using the hydrophilic coating composition of Example 1. Then, the test piece was left outdoors for a certain period of time, and the state was observed.

The results are shown in FIG. Where the coating was formed, it was very clean because the dirt was washed out by rain while it was left unattended, whereas in the place where the coating was not formed, the dirt was not washed out and it was dirty. You can see that is left.

Claims (7)

A hydrophilic coating composition containing colloidal silica and a thickener, which can be coated on an undercoat film .
When a coating having a thickness of 10 μm is formed on the white substrate, the color difference ΔE * before and after the application of the white substrate is 0.50 or less .
The viscosity measured according to JIS K5600-2-2 using a stoma viscometer is in the range of 40 to 120 KU , and
The haze of the coating formed on the glass substrate is 50% or less.
Composition for hydrophilic coating. The composition for hydrophilic coating according to claim 1, wherein the thickener is a swellable layered silicate or a water-soluble polymer. The composition for hydrophilic coating according to claim 2, wherein the thickener is synthetic smectite. The composition for hydrophilic coating according to claim 2, wherein the thickener is hydroxyethyl cellulose. The composition for hydrophilic coating according to any one of claims 1 to 4, wherein the colloidal silica is contained in an amount of 2 to 10% by mass in a solid content concentration. The hydrophilic coating composition according to any one of claims 1 to 5, further comprising a water-soluble dye. A structure comprising a substrate, an undercoat film, and a coating with the hydrophilic coating composition according to any one of claims 1 to 6, wherein the undercoat film is a heat-shielding coating film. Structure.

Images